The present invention relates to a friction material with decreased variation in friction coefficient.
The friction material such as brake pad, brake lining, clutch facing or the like used for the brake and the clutch of motorcars, railroad vehicles, industrial machines, etc. is generally made by combining and molding principal raw materials comprising reinforcing material such as asbestos, metallic fiber, iron powder or the like, friction modifier such as organic dust, metal oxide powder or the like and wear resistant solid lubricant such as graphite, molybdenum disulfide or the like with phenol resin being a thermosetting organic binder.
The friction material containing the phenol resin as a binder adsorbs, however, the moisture in atmosphere during the use because of the moisture adsorption property of phenol resin resulting in significant changes in friction and wear characteristics, which has been a problem.
As a result of investigations to solve said problem, a friction material of hardly subjected by moisture in atmosphere has been developed by the invention.